Such a hydraulic steering is, for example, known from DE 10 2007 053 024 B4. A vehicle equipped with such a steering can either be steered via the steering unit comprising a directional section, or via the steering valve. The driver will then usually activate a steering member, for example a steering hand wheel. When the driver steers the vehicle by means of the steering unit, in many cases a so called reaction behavior is desired, that is, the driver must feel through the steering hand wheel that forces are acting upon the steering motor.
However, this reaction behavior causes problems, if the vehicle is steered by means of the steering valve. Thus, in the state of the art for each steering direction the directional section comprises a first outlet, which is connected to the steering motor by means of a first pipe, and a second outlet, which is connected to the steering motor by means of a second pipe, the first pipe being, in the neutral position of the directional section, connected to a measuring section, and the first pipe being interruptible by means of the valve arrangement.
With this solution a reaction of the steering motor is achieved both if the directional section is activated and if the directional section is in a neutral position. Forces acting upon the steering motor are transferred via the first pipe to the first outlet and via the directional section to the measuring motor.
In some cases it happens that a valve gets stuck, that is, in spite of an activation signal the valve does not change its position as specified by the activation signal. If now, for example, the valve arrangement gets stuck in a closed position and interrupts the first pipe the second pipe will bypass the valve arrangement. This way the hydraulic steering can still be operated via the steering unit. The disadvantage of this solution is that the steering resistance will be higher if the valve arrangement gets stuck. At the same time such a wrong valve position cannot be directly detected during normal operation within a hydraulic steering according to the state of the art.